A socket complying with USB (Universal Serial Bus) standard is mounted to a wide range of recent information processing devices, and various peripheral devices are connected via the socket.
As the USB standard, four types of specifications of USB1.0, USB1.1, USB2.0, and USB3.0 have been established so far. USB1.1 to USB3.0 are of backward compatibility and required to correctly operate when connecting a lower standard product and an upper standard product to each other except that its function and performance are restricted by the lower standard.
Also, as one of the peripheral devices to be connected to the information processing device via the USB socket, a memory device in which a nonvolatile flash memory and a controller are mounted to a printed substrate together with a USB connector (Standard-A) and housed in a casing, which is a so-called USB memory, has been known (see Japanese Patent Application Laid-Open No. 2007-156682). As the USB memory, products complying with USB2.0 having a maximum transfer speed of 480 Mbits/s are currently predominant.
In recent years, a memory capacity of a USB memory has been steadily increasing. Also, there is a tendency that an amount of data per file handled by an information processing device is increased. Therefore, in order to realize higher speed data transfer between the information processing device and the USB memory, there is a demand for development of a USB memory complying with USB3.0 having a maximum transfer speed of 5 Gbits/s.
Since the backward compatibility is required in the USB standard as described above, the USB memory complying with USB3.0 is required to transfer data at a speed prescribed in the standard in both of the cases of data transfers at USB 3.0 or USB 2.0. However, any specific configuration for realizing the data transfer has not been proposed.